Alex Barbat Profile : Scipedia

Alex Barbat 3535

Professor Emeritus at the Department of Civil and Environmental Engineering
Universitat Politècnica de Catalunya - BarcelonaTech International Centre for Numerical Methods in Engineering

Alex Barbat 3535

Professor Emeritus at the Department of Civil and Environmental Engineering
Universitat Politècnica de Catalunya - BarcelonaTech International Centre for Numerical Methods in Engineering

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Alex Barbat's technical and research reports

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Alex Barbat's Technical Reports is an online archive aimed at collecting, preserving, and disseminating digital copies of the technical reports written by prof [...]

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Alex Barbat's monographs

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Alex Barbat's Monographs is an online archive aimed at collecting, preserving, and disseminating digital copies of the monographs written by prof Alex [...]

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Alex Barbat's chapters of books

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Alex Barbat's Research Reports is an online archive aimed at collecting, preserving, and disseminating digital copies of the research reports written by prof [...]

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Alex Barbat's articles in WoS/Scopus journals

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Alex's Barbat Journal Papers is an online archive aimed at collecting, preserving, and disseminating digital copies of the scientific papers published [...]

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Documents published in Scipedia

New Tension-Compression Damage Model for Complex Analysis of Concrete Structures
J. Paredes, S. Oller, A. Barbat

Journal of Engineering Mechanics, ASCE (2016). 142(10), 04016072, doi: 10.1061/(ASCE)EM.1943-7889.0001130

Abstract
A new damage model, based on continuum damage mechanics and simulating the opening, closing, and reopening of cracks in concrete using only one surface of discontinuity, is proposed in this article. The model complies with the thermodynamics principles of nonreversible, isothermal, and adiabatic processes. Two scalar internal variables have been defined: a tensile damage variable d+ and a compressive damage variable d−; the threshold of damage is controlled by only one surface of discontinuity and a new parameter controlling the damage variable that should be activated. This new parameter represents the ratio of tensile stress to compressive stress in the damaged material. The continuity of response under complex loads, which is one of the aims of this work, is ensured. An adequate response under different types of loads leads to the conclusion that the proposed model provides a powerful tool to numerically analyze reinforced concrete structures. Validation and illustrative examples are included in the article.
Abstract
A new damage model, based on continuum damage mechanics and simulating the opening, closing, and reopening of cracks in concrete using only one surface of discontinuity, [...]
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ACTIVE CONTROL OF NONLINEAR BASE-ISOLATED BUILDINGS
A. Barbat, J. Rodellar, E. Ryan, N. Molinares

Journal of Engineering Mechanics, ASCE (1995). 121(6), 676-684

Abstract
A hybrid seismic control system for building structures is considered, which combines a class of passive nonlinear base isolator with an active control system. The active control forces are applied to the structural base with the objective of reducing its absolute displacements. An adaptive control law is formulated to compute the control forces to assure a form of stable behavior of the system under seismic excitation and in the presence of uncertainties in the characteristics of the building and the base isolator. Numerical simulations are performed to assess the effectiveness of the hybrid control system. The global behavior of the structurebase-isolator system is such that the absolute base displacement is significantly reduced, the price paid being a slight increase of the response of the structure.
Abstract
A hybrid seismic control system for building structures is considered, which combines a class of passive nonlinear base isolator with an active control system. The active [...]
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High Damping Rubber Model for Energy Dissipating Devices
P. Mata, R. Boroschek, A. Barbat, S. Oller

Journal of Earthquake Engineering (2007). 11, 231–256, DOI: 10.1080/13632460601123214

Abstract
This work presents the results of a study carried out to characterize the mechanical response of a high damping rubber to be used in designing and constructing energy dissipating devices and base isolators for controling strong vibrations in civil engineering structures. A new parametric model of the elastomer is proposed to be employed in the design procedure and structural analysis of passive controlled structures. The parameters of the model are calibrated using experimental data obtained from tests on rubber specimens under different loading paths. The main dissipating energy mechanisms of the rubber are identified. The proposed model is able to reproduce those main mechanisms as well as geometric second order effects such as tension stiffening due to the effect of axial strains in the response. The response predicted by the proposed model is compared with that obtained from experimental tests and from the Kelvin and plasticity models.
Abstract
This work presents the results of a study carried out to characterize the mechanical response of a high damping rubber to be used in designing and constructing energy dissipating [...]
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Earthquake Loss Assessment for Integrated Disaster Risk Management
O. Cardona, M. Ordaz, L. Yamin, M. Marulanda, A. Barbat

Journal of Earthquake Engineering (2008). 12(S2), 48–59, DOI: 10.1080/13632460802013495

Abstract
Understanding probable losses and reconstruction costs due to earthquakes creates powerful incentives for countries to develop planning options and tools to cope with risk, including allocating the sustained budgetary resources necessary to reduce those potential damages and safeguard development. A specific catastrophic risk model has been developed to evaluate, building by building, the probabilistic losses and pure premiums of different portfolios, taking into account the seismic microzonation of cities. This model has been used to evaluate the fiscal contingency liabilities of the government and to build an optimal structure for risk transfer and retention, considering contingent credits, reserve funds, insurance/reinsurance, and cat bonds. Lastly, the model allows the evaluation of an exceedance probability curve of benefit-cost ratio, providing an innovative and ground-breaking tool for decision makers to analyze the net benefits of the risk mitigation strategies, such as earthquake retrofitting and seismic code enforcement. This article describes the model and the derived abovementioned tools, using the results of loss scenarios and the strategies implemented in some earthquake prone urban centers.
Abstract
Understanding probable losses and reconstruction costs due to earthquakes creates powerful incentives for countries to develop planning options and tools to cope with risk, [...]
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Estimation of Probabilistic Seismic Losses and the Public Economic Resilience—An Approach for a Macroeconomic Impact Evaluation
O. Cardona, M. Ordaz, M. Marulanda, A. Barbat

Journal of Earthquake Engineering (2008). 12(S2), 60–70, DOI: 10.1080/13632460802013511

Abstract
The Disaster Deficit Index (DDI) measures country risk from a macroeconomic and financial perspective, according to possible catastrophic events. The DDI captures the relationship between the demand for contingent resources to cover the maximum probable losses and the public sector’s economic resilience; that is, the availability of internal and external funds for restoring affected inventories. For calculating potential losses, the model follows the insurance industry in establishing a probable loss, based on the critical impacts during a given period of exposure, and for the economic resilience the model computes the country’s financial ability to cope with the situation taking into account: the insurance and reinsurance payments; the reserve funds for disasters; the funds that may be received as aid and donations; the possible value of new taxes; the margin for budgetary reallocations; the feasible value of external credit; and the internal credit the country may obtain. Access to these resources has limitations and costs that must be taken into account as feasible values according to the macroeconomic and financial conditions of the country. This article presents the model of DDI and proposes it as a simple way of measuring a country’s fiscal exposure and potential deficit—or contingency liabilities—in case of extreme disasters to guide the governmental decisionmaking from economic, financial, and disaster risk reduction perspectives.
Abstract
The Disaster Deficit Index (DDI) measures country risk from a macroeconomic and financial perspective, according to possible catastrophic events. The DDI captures the relationship [...]
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VISCOUS DAMAGE MODEL FOR TIMOSHENKO BEAM STRUCTURES
A. Barbat, S. Oller, E. Oñate, A. Hanganu

International Journal of Solids Structures (1997). 34(30), 3953-3976

Abstract
A local damage constitutive model based on Kachanov’s theory is used within a finite element frame and applied to the case of 2D and 3D Timoshenko beam elements. The model takes into account viscous effects, thus allowing damping to be considered in a rigorous way. A damage index based on potential energy criteria, useful in evaluating the behaviour of structures or of parts of structures, is proposed. The procedure is applied to estimate the damage produced by seismic actions in reinforced concrete building structures, whose response is computed by using a non-linear Newmark-type incremental time integration scheme. Three numerical examples are included; one of them compares results obtained by using the proposed model with results of a laboratory test.
Abstract
A local damage constitutive model based on Kachanov’s theory is used within a finite element frame and applied to the case of 2D and 3D Timoshenko beam elements. The [...]
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Analysis of Ultra Low Cycle Fatigue problems with the Barcelona plastic damage model and a new isotropic hardening law
X. Martínez, S. Oller, L. Barbu, A. Barbat, A. Jesus

International Journal of Fatigue (2015). 73, 132–142, http://dx.doi.org/10. 1016/j.ijfatigue.2014.11.013

Abstract
This paper presents a plastic-damage formulation and a new isotropic hardening law, based on the Barcelona plastic damage model initially proposed by Lubliner et al. (1989) [1], which is capable of predicting steel failure due to Ultra Low Cycle Fatigue (ULCF). This failure mechanism is obtained when the material is subjected to cyclic loads and breaks after applying a very low number of cycles, usually less than hundreds. The failure is driven by the plastic response of the material, and it is often predicted based on the plastic strains applied to it. The model proposed in this work has been formulated with the objective of predicting accurately the plastic behavior of the material, as well as its failure due to ULCF. This is achieved taking into account the fracture energy dissipated during the whole loading process. This approach allows the simulation of ULCF when it takes place due to regular cyclic loads or non-regular cyclic loads, as it is the case of seismic loads. Several simulations are conducted in order to show the capabilities of the formulation to reproduce the mechanical response of steel when it is subjected to regular and non-regular cyclic loads. The formulation is validated comparing the numerical results with several experimental tests made o n X52 steel specimens. The agreement between the numerical and experimental results asses the validity of the proposed model to predict the plastic behavior of steel and its failure due to Ultra Low Cycle Fatigue.
Abstract
This paper presents a plastic-damage formulation and a new isotropic hardening law, based on the Barcelona plastic damage model initially proposed by Lubliner et al. (1989) [...]
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Validation on large scale tests of a new hardening–softening law for the Barcelona plastic damage model
L. Barbu, X. Martinez, S. Oller, A. Barbat

International Journal of Fatigue (2015). 81, 213- 226, doi:10.1016/j.ijfatigue.2015.07.031

Abstract
This paper presents the results of finite element simulations made on a bent pipe subjected to an in-plane variable cyclic displacement combined with internal pressure. Special emphasis is put on the capacity of the model to illustrate different failure modes depending on the internal pressure applied on the pipe. The results of the numerical analyses will be compared to experimental ones. The constitutive model used for the simulation of Ultra Low Cycle Fatigue (ULCF) loading and the hardening–softening law used are only briefly touched upon. The monotonic behavior of a large diameter pipe, as obtained from the constitutive model proposed, is also shown and compared to experimental results under two different loading conditions. The total axial load at failure for this case resulted in less than 10% error as compared to the experiments. Regarding the ULCF in-plane bending simulations conducted on a 16-in. 90º elbow, the results were in good agreement with the experimental test in terms of force–displacement hysteresis loops and total fatigue life of the specimen. An analysis of the dependence of the failure mode to the internal pressure applied has been conducted, showing that the formulation is capable of obtaining both habitual failure types.
Abstract
This paper presents the results of finite element simulations made on a bent pipe subjected to an in-plane variable cyclic displacement combined with internal pressure. Special [...]
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Behaviour of the interface between concrete and FRP using serial/ parallel mixing theory
M. Molina, J. Cruz, S. Oller, A. Barbat, L. Gil

INGENIERÍA E INVESTIGACIÓN (2011). 31(3), 26-39

Abstract
Experimental research has shown that one of the key factors affecting the behaviour of reinforced concrete structures strengthened with externally-bonded fibre-reinforced polymer (FRP) is the bonding behaviour between concrete and FRP laminates. As a complement to experimentation, this paper proposed the use of serial/parallel mixing theory in numerical simulation, which is a tool for studying the behaviour of the concrete-FRP epoxy interface. An example is presented which analyses beam test simulation results and compares them with the experimental results.
Abstract
Experimental research has shown that one of the key factors affecting the behaviour of reinforced concrete structures strengthened with externally-bonded fibre-reinforced [...]
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FINITE ELEMENT ANALYSIS OF BASE ISOLATED BUILDINGS SUBJECTED TO EARTHQUAKE LOADS
O. Salomón, S. Oller, A. Barbat

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING (1999). 46, 1741-1761

Abstract
A finite element formulation modelling hyperelastic quasi-incompressible rubber-like materials (elastomers) is developed which takes into account large displacements and large elastic strains as well as inelastic effects. The capacity of laminated rubber-like materials to support high loads in compression and large displacements in shear is the principal reason for their use in devices for seismic base isolation of structures. The energy-dissipation capacity of these devices is increased by using high damping rubber, which is an elastomer incorporating carbon black particles, or having lead-plug insertion. The Ogden strain energy function has been used as a basis for the material model implemented in a total Lagrangian formulation, the strain being decomposed into its deviatory and volumetric parts and the pressure variable being condensed at element level. Mooney-Rivlin and neo-Hooke strain energy functions can also be used by simply changing the parameters of the model. The stress-strain hysteresis, which appears when these devices are subjected to dynamic or quasi-static cyclic loads, has been modelled by frequency dependent viscoelastic and plastic constitutive models. The bearings have been modelled by means of an equivalent single element capable of describing the composite behaviour of the actual isolation system. The proposed model is validated using available experimental results and it is proved to be a powerful tool in dealing with different bearings. Finally, results for a six-storey base isolated building subjected to the El Centro earthquake are given.
Abstract
A finite element formulation modelling hyperelastic quasi-incompressible rubber-like materials (elastomers) is developed which takes into account large displacements and large [...]
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Articles (Documents not available in Scipedia)

Analysis of Ultra Low Cycle Fatigue problems with the Barcelona plastic damage model and a new isotropic hardening law
X Martinez, S Oller, LG Barbu, AH Barbat, AMP De Jesus

International Journal of Fatigue 73, 132-142, 2015
Hybrid loss exceedance curve (HLEC) for disaster risk assessment
CA Velásquez, OD Cardona, MG Mora, LE Yamin, ML Carreño, ...

Natural hazards 72 (2), 455-479, 2014
Capacity, fragility and damage in reinforced concrete buildings: a probabilistic approach
YF Vargas, LG Pujades, AH Barbat, JE Hurtado

Bulletin of earthquake engineering 11 (6), 2007-2032, 2013
Seismic safety of RC framed buildings designed according to modern codes
JC Vielma, Barbat A., Oller S.

Journal of Civil Engineering and Architecture 5 (7), 2011
Probabilistic seismic risk assessment for comprehensive risk management: modeling for innovative risk transfer and loss financing mechanisms
OD Cardona, MG Ordaz, L Yamín, S Arámbula, MC Marulanda, A Barbat

The 14th World Conference on Earthquake Engineering, 2008
Viscous damage model for Timoshenko beam structures
AH Barbat, S Oller, E Onate, A Hanganu

International Journal of Solids and Structures 34 (30), 3953-3976, 1997

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COLLECTIONS

Alex Barbat's technical and research reports

Alex Barbat's monographs

Alex Barbat's chapters of books

Alex Barbat's articles in WoS/Scopus journals

Documents published in Scipedia

New Tension-Compression Damage Model for Complex Analysis of Concrete Structures

ACTIVE CONTROL OF NONLINEAR BASE-ISOLATED BUILDINGS

High Damping Rubber Model for Energy Dissipating Devices

Earthquake Loss Assessment for Integrated Disaster Risk Management

Estimation of Probabilistic Seismic Losses and the Public Economic Resilience—An Approach for a Macroeconomic Impact Evaluation

VISCOUS DAMAGE MODEL FOR TIMOSHENKO BEAM STRUCTURES

Analysis of Ultra Low Cycle Fatigue problems with the Barcelona plastic damage model and a new isotropic hardening law

Validation on large scale tests of a new hardening–softening law for the Barcelona plastic damage model

Behaviour of the interface between concrete and FRP using serial/ parallel mixing theory

FINITE ELEMENT ANALYSIS OF BASE ISOLATED BUILDINGS SUBJECTED TO EARTHQUAKE LOADS

Articles (Documents not available in Scipedia)

Analysis of Ultra Low Cycle Fatigue problems with the Barcelona plastic damage model and a new isotropic hardening law

Hybrid loss exceedance curve (HLEC) for disaster risk assessment

Capacity, fragility and damage in reinforced concrete buildings: a probabilistic approach

Seismic safety of RC framed buildings designed according to modern codes

Probabilistic seismic risk assessment for comprehensive risk management: modeling for innovative risk transfer and loss financing mechanisms

Viscous damage model for Timoshenko beam structures

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